In general, as eyeglass frames, a rim frame (full rim frame), a rimless frame (two-point frame), a grooved frame (half-rim and Nylor) and the like are known.
In the grooved frame, for example, a retention groove which extends in the circumferential direction is formed on an outer circumferential face of a lens, a half-rim is firmly affixed to the upper side of the lens (eyeglass lens), and Nylor which is supported by both ends of the half-rim is arranged in the retention groove in the lower side of the lens, so that the lens is affixed to the half rim by Nylor.
For this grooved frame, it is necessary to form the retention groove extending in the circumferential direction on the outer circumferential face of the lens. This retention groove is obtained by forming a circular groove extending in the circumferential direction on the outer circumferential face of the lens by a cutter and the like after the rim of the circular unprocessed eyeglass lens is formed into the lens (eyeglass lens) shape by a lens grinder according to lens shape data.
Meanwhile, a lens shape measurement device disclosed in JP H10-166250A is known. The lens shape measurement device disclosed in JP H10-166250A includes a lens frame holder provided in the main body of the measurement device, a rotation base provided in a frame of the main body in a horizontally rotatable manner, and a rotation and driving motor which rotates and drives the rotation base. The lens shape measurement device also includes a slider mounted on the rotation base in a linearly movable manner in the horizontal direction, a measurement shaft mounted on the slider in a vertically movable manner, and a measuring element for a lens frame which is set in the upper end portion of the measurement shaft and engages with a V-groove of a lens frame of a rim frame.
In this lens shape measurement device, a moving radius ρi (a change in a distance from a geometric center of a lens frame to a V-groove) relative to a rotation angle θi of the rotation base and a displacement Zi in the up and down direction can be obtained as lens frame shape data (θi, ρi, Zi) by moving the measuring element for a lens frame along the V-groove.
As the above lens shape measurement device, a device in which a lens holder (lens holding unit) which holds a lens is detachably attached to a main body and a measuring element for a lens is arranged in a slider to freely rise up and fall is known. In this lens shape measurement device, the measuring element for a lens is set up and has contact with the outer circumferential face of the lens held by the lens holder, and the rotation base horizontally rotates by the rotation and driving motor, so that the measuring element for a lens is slidably moved in the circumferential direction along the outer circumferential face of the lens, and the moving radius ρi (a change in a distance from a geometric center or an optical center of a lens to a rim) of the lens relative to the rotation angle θi of the rotation base can be obtained as lens circumferential face shape data (θi, ρi).
In this lens shape measurement device, the shape data of the lens frame is obtained as the above-described three-dimensional shape data; however, the shape data of the lens is two dimensionally obtained as a moving radius ρi relative to a rotation angle θi.
Consequently, in order to process the retention groove on the lens, it is necessary to hold an unprocessed eyeglass lens between lens rotation shafts which are mounted on a lens grinder in series, rotate the lens rotation shafts and the unprocessed eyeglass lens together at a predetermined angle Δθ before grinding the rim portion of the unprocessed eyeglass lens according to the circumferential face shape data (θi, ρi) by a grinding stone, and measure positional data in the direction along the lens rotation shafts of the front side refracting surface and the back side refracting surface in the moving radius ρi of the unprocessed eyeglass lens by an edge thickness measurement unit.
Meanwhile, when ordering eyeglasses in opticians, for example, it is general to select one's favorite eyeglasses from displayed sample eyeglasses. In an actual situation for such sample eyeglasses, demo-lenses (dummy lenses) are attached to a frame or a rimless frame. The circumferential face (edge face) of the demo-lenses attached to the frame (rim) is formed in a shape along the three-dimensional shape of the frame (rim).
However, an actual eyeglass lens has a difference in a curvature of a refracting surface according to a prescription of the eyeglasses, or in an edge thickness according to a rotation center of a lens in the grinding of the rim of the lens. For this reason, in a grooved frame, when mounting an actual eyeglass lens on a half-rim, a bending process is performed to the half rim according to the rim shape of the eyeglass lens.
However, it is desirable to mount the eyeglass lens on the half-rim frame without performing such a bending process for a half-rim. In order to achieve that, it is necessary to measure a three-dimensional shape of a half-rim; however, in the above-described measurement device, a three-dimensional shape of a half-rim can not be measured.
It is, therefore, an object of the present invention to provide a lens shape measurement device which can specify a three-dimensional shape of a half-rim frame even in a grooved frame by obtaining a circumferential face shape and a curvature of a refracting surface of a lens such as a demo-lens.